Falcon Heavy Flight Animation
I'm not quite sure whether this is what is really being planned, or whether someone's imagination got loose. Recovering the boosters by having them land vertically in a reversal of their launch is brilliant, if you can make it work. Once the booster has consumed the bulk of its fuel it will weigh practically nothing, which means slowing it back down would take hardly any fuel at all. Being able to recover the boosters could save you some money on your next launch. You do have a weight penalty on launch from the landing gear and the fuel needed for deceleration and landing. And the engines would need to be more durable. A rocket motor designed for one use is not the motor you want to use in a reusable rocket booster. It's still the best idea for rockets I've seen in a long time.